Combined control of fluid adsorption capacity and initial permeability on coal permeability

The variations of strain and permeability of coal were systematically studied through the physical simulation of N2 and water injection.The effects of fluid adsorption capacity and initial permeability on strain,permeability and the dominant effect of pore pressure were discussed.The adsorption strain and strain rate of coal during water injection are significantly higher than those during N2 injection.An edge of free adsorption exists in the early phase of N2 and water injection,which is related to fluid saturation.Within this boundary,the strain rate and pore pressure are independent.Moreover,the injec-tion time of initial stage accounts for about 20%of the total injection time,but the strain accounts for 70%of the total strain.For water injection,this boundary is about half of water saturation of coal.Besides,the influence of pore pressure on permeability is complex,which is controlled by adsorption capacity and initial permeability of coal.When the initial permeability is large enough,the effect of adsorption strain on permeability is relatively weak,and the promoting effect of pore pressure on fluid migration is dominant.Therefore,the permeability increases with increasing pore pressure.When the initial permeability is relatively low,the pore pressure may have a dominant role in promoting fluid migration for the fluid with weak adsorption capacity.However,for the fluid with strong adsorption capacity,the adsorption strain caused by pore pressure may play a leading role,and the permeability reduces first and then ascends with increasing pore pressure.

NANOCRYSTALLINE STRUCTURE AND INITIAL PERMEABILITY OF ANNEALED Fe_(73.5)Cu_(1)W_(3)Si_(13.5)B_(9) Alloy

The nanocrystalline structure of annealed Fe73.5 Cu1 W3Si13.5B9 alloy has been investigated by using the XRD and the TEM methods. The relation between the initial permeability and the microstructure of the annealed alloy has been discussed. The crystalline phase in annealed Fe73.5 Cu1 W3Si13.5B9 alloy is the α-Fe(Si) phase with DO3 superstructure. The volume fraction, Si content and degree of order of the αFe(Si) phase increase with increasing annealing temperature. In the temperature range of 490-570℃, the α-Fe(Si) phase has a size of 13 nm, and its grain number increases as the annealing temperature is increased. The DO3 ordered region in the α-Fe(Si) grain is spherical approximately, and its size increases as the annealing temperature increases. The size of the DO3 ordered region is 12.8 nm at the temperature of 570℃,which is close to that of the α-Fe(Si) grain. There is obvious change in the structure of the residual amorphous phase during annealing, and the nearest atomic distance and the short-range order of residual amorphous phase reach maximum and minimum at 530℃, respectively. The initial permeability of annealed Fe73.5 Cu1 W3Si13.5 B9 alloy is not only dependent on the size, volume fraction and Si content of the α-Fe(Si) phase but also related to the structure state of the residual amorphous phase.

Rolling contact fatigue nondestructive testing system for a bearing inner ring based on initial permeability

Due to the fact that rolling contact fatigue is not easily detected, and residual life is not easily evaluated in the early stage of bearing life, a nondestructive testing method based on initial permeability is proposed. By analyzing the crack propagation mechanism, a fatigue state detection system based on differential signals is designed. A simulation model of the detection of the inner ring of the pulse signal is established by using the electromagnetic field simulation software. The effects of the height of the coil, the inner and outer diameter, the number of coil turns, the diameter and the height of the ferrite core of the probe on the differential value of the detection signal are simulated. The parameter combination of the maximum difference value of the signal is used as the structural size of the sensor, and the detection sensor is designed and fabricated. Moreover, the bearing fatigue test system is designed, and the bearing is tested. The results show that the system has good detection ability for rolling contact fatigue and verifies the mechanism and trend of crack propagation in the inner ring of the bearing.

Complex Permeability of Ferrites as Intrinsic and Extrinsic Properties

CIP （complex initial permeability） spectra of PF （polycrystalline ferrite） are studied both as intrinsic and extrinsic properties. In the former case, main steps of modeling, based on effects coming from polycrystal grain sizes distribution and defects, are described. The obtained relations work well in practice for PF with more or less normal MS （microstructure） and no size effects. Besides, fundamental connection between parameters of CIP and MS is found. Another case--PF with possible size effects （MnZn-ferrites） are studied experimentally for different sizes of cores, unveiling the dependence of phenomena on： dimensions of cross-section, number of turns, width of nonmagnetic gap.

Effect of sintering process on microstructure and magnetic properties of high frequency power ferrite

An oxide ceramic process was adopted to prepare high frequency manganese-zinc(MnZn)power ferrite.In combination with the microstructure analysis of material,the influences of sintering process on initial permeability(μ_(i))and high frequency loss in unit volume(P_(cv))of MnZn power ferrite were investigated.The results show that in order to obtain fine microstructure and high frequency properties,the preferable sintering temperature and atmosphere are 1230℃and oxygen partial pressure(P_(O_(2)))of 4%,respectively.

THREE NEW Fe-BASED MICROCRYSTALLINE ALLOYS WITH SUPERIOR MAGNETIC PROPERTIES

Three new Fe-based microcrystalline alloys,i.e.,Fe_(73.1)Cu_(1.2)Nb_(3.2)Si_(12 5)B_(10), Fe_(73)Cu_1Nb_(1.5)Mo_2Si_(12.5)B_(10) and Fe_(73)Cu_1Zr_3C_(0.5)Mo_Si_(12.5)B_(10),were developed with su- perior magnetic properties.e.g.,high relative initial permeability of μ_i^15×10~4,low coercivity of H_c1.0A/m,high effective permeability and low core losses in a consid- crable wide frequency range and high pulse-magnetic permeability under narrow pulse. The optimum value of relative effective permeability,μ_5~1 is 16×10~4 under condition of f=1 kHz and H_m=0.4 A/m.The optimum values of core loss reach 57.9 30.2 and 68 W/kg under condition of f=50.100.100 KHz and B_m=0.5,0.2,0.3 T,respectively. These three alloys have superior stability of magnetic properties.Initial permeability may be not changed during heating at 130℃ up to 216 h.The main crystalline phase is ordered phase Fe_((75)+y)Si_((25)-y) which is ultrafine particles of average size 10—20 nm.

Sintering Temperature Dependent Magnetic and Dielectric Properties of Polycrystalline xBa_0.95Sr_0.05TiO₃-(1 - x)BiFe_0.90Gd_0.10O₃Ceramics

Polycrystalline xBa0.95Sr0.05TiO3-(1 - x)BiFe0.90Gd0.10O3 ceramics were prepared by standard solid state reaction technique using the solid solution of BaCO3, SrCO3, TiO2, Bi2O3, Fe2O3 and Gd2O3. The compound is a BiFeO3 based multiferroic material which contains both magnetic and electric properties. The synthesized ceramics noticed better properties than xBaTiO3-(1 - x)BiFeO3 because of adding rare earth element Gd which have higher magnetic moment than Fe. The prepared samples were sintered at 900˚C, 950˚C and 1000˚C for 1 h. The effect of sintering temperature on density of the compound, complex initial permeability, dielectric properties and complex impedance analysis was reported in this article. Density of the ceramics was found to be enhanced with the rise in sintering temperature which implied porosity of the compound decreased when sintering temperature was increased. Enhanced complex initial permeability was noticed for the samples up to 950˚C and this might be attributed to reducing the motion of domain wall when the ceramics were sintered above 950˚C. Value of dielectric constant increased whereas dielectric loss decreased and these modifications might be expected because of changing density and grain size due to the variation of sintering temperature. Grain resistance (resistance due to grains) was determined from complex impedance analysis and it reduced with the rise in sintering temperature. The studied multiferroic material exhibited weak ferromagnetism but is an alternative product of environmental hazard lead (Pb) based multiferroic material and it is expected to be environment friendly.

Effect of Cu Incorporation on Structure, Densification and Magnetic Properties of Polycrystalline Li_<i>x</i>Ni_0.2Zn_{0.8-2<i>x</i>}Fe_2+<i>x</i>O₄Ceramics

The polycrystalline LixNi0.2Zn0.8-2xFex+2O4 and LixNi0.1Cu0.1Zn0.8-2xFex+2O4 (x = 0.0, 0.1, 0.2, and 0.3) ferrites were synthesized by the standard solid-state reaction method. The compound was sintered at 1150˚C for 5 hours. The effect of Cu substitution and its impact on the crystal structure, microstructure, complex initial permeability and magnetization of the Ni-Zn ferrites were studied. The effect of Li+ incorporation on the properties mentioned above was also investigated. X-ray diffraction patterns of the samples indicated a single cubic spinel structure for both the compound. No effect of Cu addition on crystal structure was observed. The density of the ferrites was found to be enhanced because of adding Li whereas the porosity of the samples decreased with the content of Li ions. The average value of grain size increased with the addition of Li content. The samples having Cu ions formed bigger size grains. Frequency-dependent complex initial permeability, loss tangent, and relative quality factor were studied at room temperature using an Impedance analyzer in the range of 100 Hz - 120 MHz regions. In the low-frequency region, the prepared samples exhibited a high value of permeability and after a certain frequency, the permeability falls. The value of permeability enhanced with the increase in Li whereas loss tangent was found to be reduced. The relative quality factor graphs described that the compound has excellent frequency stability up to a certain frequency which is suitable to be used in inductors, resistors, capacitors, etc. Initial permeability for LixNi0.1Cu0.1Zn0.8-2xFex+2O4 ferrites was found high than LixNi0.2Zn0.8-2xFex+2O4 which might be attributed to having bigger size grains of Cu containing samples because of easy movement of domain wall in bigger size grains. The values of saturation magnetization (Ms) were calculated for both compounds from M-H hysteresis loops and it enhanced with the increase in Li content which might be related to the modification of predominant exchange interactions between the cations. The Cu-containing compound exhibited higher values of saturation magnetization. The cation distribution reflects this increment because ferromagnetic Ni2+ and paramagnetic Cu2+ ions occupied in the B-sites and the diamagnetic Zn and paramagnetic Li occupied in the A-sites;therefore, net magnetic moments increased gradually. The studied materials might be used as an alternative to Pb-based compounds and would be environment friendly.

Neuroinflammation in glaucoma：soluble tumor necrosis factor alpha and the connection with excitotoxic damage

Inflammation is a complex and highly regulated response that occurs early after infection or injury.This process is initiated by cells of the immune system to re-establish tissue homeostasis.When the injury is persistent,however,chronic inflammation leads to overproduction of noxious mediators that contribute to cell dysfunction and death.

Room-temperature and high-temperature magnetic permeability of Co-doped nanocrystalline alloys

Influence of composition and annealing temperature on structure and magnetic properties of amorphous and nanocrystalline Fe78.4-xCoxSi9B9Nb2.6Cu1 （x=27.4, 40.0, 51.0, 78.4） alloys was investigated by X-ray diffraction （XRD） and the temperature dependence of permeability. According to the initial crystallization temperature （Tx1） from differential scanning calorimetry （DSC） curves of as-quenched amorphous alloys, 490-700 ℃ isothermal annealing was carded out to obtain the characteristic nanocrystalline structure. Furthermore, the soft magnetic properties were measured by temperature evolution of magnetic permeability to obtain the correlation between Co content, annealing temperature and magnetic permeability. The results show that, on the one hand, the annealing temperature exerts a significant effect on phase structure and initial permeability （μi）. The higher-temperature （from 550 to 610 ℃） annealed Co content nanocrystalline samples can remain higher μi at elevated temperature. On the other hand, partial substitution Fe by Co can improve the high-temperature magnetic stability;however, the room-temperature permeability of higher Co content alloys decreases obviously at the same time. This phenomenon was analyzed from the viewpoint of the saturation magnetic induction （Bs）, magnetic anisotropy （〈K〉） and magnetostriction （λs）.

Influence of Boron Content in Iron Oxide on Performance of Mn-Zn Ferrites

The ferrites of PC30 （Mn-Zn ferrites） were prepared by using a dry processing route. The effect of Mn-Zn ferrites doped with H3BO3 was investigated on the basis of microstructure analysis. The results of the samples doped with H3BO3 less than 5 × 10^-5 showed that the doping had no significant effect on power loss, initial permeability, fine grain microstructure, and density of Mn-Zn ferrites. With the further increase in H3BO3 doping （up to 1 × 10 ^-4 ）, the microstructure of Mn-Zn ferrites is in the critical state between fine grain and ＂sandwich＂, and the initial permeability and density of Mn-Zn ferrites begin falling quickly; the increased H3BO3 doping also results in deteriorated power loss properties. Thus, the control of the boron content in iron oxide is of utmost importance for the quality of Mn-Zn ferrites in producing process.

Geomagnetic Shielding Property and Mechanism of Fe–Ni Laminated Composite

Ni layers were deposited on the two sides of pure Fe substrate by using electroplating to form Ni/Fe/Ni diffusion couple. After diffusion heat treatment, Fe-Ni laminated composite was obtained with Fe-Ni alloy/Fe/Fe-Ni alloy structure. The results indicate that the Fe-Ni layers combine well with the substrate and the Fe-Ni/Fe interface presents an interlocking microstructure with small-size grains. The concentration of element Ni in the Fe-Ni layer decreases from surface to interior exhibiting a gradient distribution. Geomagnetic shielding factor （SF） of Fe-Ni laminated composite can reach as high as 22.6, which is about seven times of that of pure Fe substrate. Mathematical equation of SF for laminated structure was derived according to magnetic circuit and resistance theory. The theoretical expression reveals that parameters such as the thickness and magnetic permeability of the shield material play an important role in the magnetic shielding behavior and the theoretical calculation results of SF coincide well with our experimental values.